The tumor suppressor protein p53 is a sequence specific transcription factor and plays a central role in the regulation of several cellular processes, including cell cycle and growth arrest, apoptosis, DNA repair, senescence, angiogenesis, and innate immunity. The Mouse Double Minute 2 (MDM2) protein (or its human homolog also known as HDM2) acts to down-regulate p53 activity in an auto-regulatory manner, and under normal cellular conditions (absence of stress), the MDM2 protein serves to maintain p53 activity at low levels. MDM2 directly inhibits the transactivation function of p53, exports p53 out of the nucleus, and promotes proteasome-mediated degradation of p53 through its E3 ubiquitin ligase activity.
Deregulation of the MDM2/p53 balance by overexpression of MDM2 or by p53 mutation or loss leads to malignant transformation of normal cells. Presently p53 is known to play a key role in practically all types of human cancers, and the mutation or loss of the p53 gene can be identified in more than 50% of all human cancers worldwide. Analysis of 28 different types of human cancers in nearly 4,000 human tumor samples showed that MDM2 is amplified in 7% of human cancers and that MDM2 overexpression by amplification and p53 mutations are largely mutually exclusive (Momand et al., Nucleic Acid Res (1998) 26:3453-3459).
Because of the powerful tumor suppressor function of p53, reactivation of p53 has been long sought as a potentially novel cancer therapeutic strategy. In tumor harboring wild-type p53, MDM2 is the primary cellular inhibitor of p53 activity, and overexpression of MDM2 was found in many human tumors. Since MDM2 inhibits p53 through a direct protein-protein interaction, blocking this interaction using small molecules was pursued in several academic and industrial pharmaceutical laboratories in the last decade. A variety of non-peptide, drug-like small molecule as e.g. imidazole compounds (e.g. Nutlins or RG7112), benzodiazepinedione compounds, spirooxindole compounds (e.g. MI-219), substituted piperidines, pyrrolidinone compounds (e.g. PXN820-dl) and modifications thereof have been selected and designed in order to block MDM2/p53 interaction as a means to reactivate p53 in cells (Vassilev et al., Science (2004) 303:844-848; Grasberger et al., J Med Chem (2005) 48:909-912; Parks et al., Bioorg Med Chem Lett (2005) 15:765; Ding et al., J Am Soc (2005) 127:10130-10131; WO 2010/028862, U.S. Pat. No. 7,884,107, WO 2008/119741). A number of potent MDM2/p53 inhibitors have been evaluated in animal models of human cancer for their anti-tumor activity (Vassilev et al., Science (2004) 303:844-848; Tovar et al, Cancer Res (2013) 73 (8): 2587-2597; Ding et al, Journal of Medicinal Chemistry (2013) 56 (14): 5979-5983; Rew et al, Journal of Medicinal Chemistry (2012) 55: 4936-4954; Sun et al, Journal of Medicinal Chemistry (2014) 57 (4): 1454-1472).
In the pediatric preclinical testing program (PPTP) of the NCI, early evidence for high level anti-proliferative activity of RG7112, an inhibitor of the MDM2-p53 interaction, could be observed in vitro and in vivo. In particular, RG-7112 showed cytotoxic activity with lower median IC50 values for p53 wild-type vs. p53 mutant cell lines (Carol et al., Pediatric Blood and Cancer (2013) 60(4):633-641). Moreover, RG-7112 induced tumor growth inhibition in solid tumor xenograft models and was particularly efficacious in in acute lymphoblastic leukemia (ALL) xenograft models with mixed-lineage leukemia (MLL) rearrangement, (Carol et al., Pediatric Blood and Cancer (2013) 60(4):633-641). Additionally, the antiproliferative and proapoptotic activity of RG7112 has been observed in human acute myeloid leukemia (AML) and human prostate tumor xenograft models harboring p53 wild-type (Tovar et al, Cancer Res (2013) 73 (8): 2587-2597).
Accordingly, small molecule inhibitors of the MDM2 protein interactions offer an important approach towards cancer therapy, either as a single agent, or in combination with a broad variety of anti-tumor therapies and thus, there is the need for further MDM2 inhibitors which can be useful in the treatment of cancer.
The following prior art documents disclose spiro oxindole compounds as inhibitors of MDM2-p53 interaction:
WO 2007/104664; WO 2007/104714; WO 2008/141917; WO 2008/141975; WO 2009/077357; WO 2009/080488; WO 2010/084097; WO 2010/121995; WO 2011/067185; WO 2011/101297; WO 2011/134925; WO 2012/038307; WO 2012/022707; WO 2012/116989; WO 2006/091646; WO 2008/036168; WO 2011/060049; WO 2012/065022; WO 2012/155066; WO 2010/028862; WO 2011/153509, WO 2012/121361, WO 2015/155332, WO 2016/001376 and WO 2016/026937.
The aim of the present invention is to provide new compounds which can be used for the prevention and/or treatment of a disease and/or condition characterised by excessive or abnormal cell proliferation, especially a disease and/or condition wherein the inhibition of the interaction between MDM2 and p53 is of therapeutic benefit.
The compounds according to the invention are characterised by a powerful inhibitory effect on the interaction between MDM2 and p53 and in turn a high in vitro efficacy against tumour cells, e.g. osteosarcoma, ALL etc., which is mediated through the inhibition of the interaction between MDM2 and p53 and is the prerequisite for a corresponding efficacy in in vivo models and future patients. In addition to the inhibitory effect and cellular potency the compounds show good PK properties and selectivity against p53 mutant cell lines. Furthermore, they have good metabolic stability which is a pivotal requirement for an active pharmaceutical ingredient to reach its place of action and allow for a long-lasting efficacy. Finally, and in contrast to many compounds known in the prior art, the compounds have good chemical stability, i.e. they are for example less prone to epimerisation, a problem identified for many known representatives of spiro oxindoles in the prior art (see e.g. Zhao et al. J. Am. Chem. Soc 2013, 135, 7223-7234; Shu et al. Org. Process Res. Dev. 2013, 17, 247-256; WO 2012/065022). It is also emphasized that building up the scaffolds of compounds (I), i.e. the scaffolds of each subgroup (Ia), (Ib) and (Ic), is in itself unprecedented and needs highly sophisticated synthetic approaches to obtain these compounds of high structural complexity.